On my NBAFB, Column 9 of my lamp matrix comes on with all the other columns. For instance, if I’m on a single lamp test lighting col 1 row 1, then col 9 row 1 comes on too.

When I unplug J121, and measure voltage between pin 9 and ground, I get steady 18v. I don’t think this is right, it’s much higher than I get for the other pins. How do I troubleshoot what’s wrong in the board? I’m not sure how to read the schematics, would Q97 be the likely culprit?

Also, some of the led bulbs in column 9 are blown and look like they’ve seen more ?voltage? than they should.

Any help appreciated. I’m a novice troubleshooting board problems.

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Awesome, thanks for reply. I’ll take closer look at the link and do the continuity test later tonight. In meantime, my very simplistic/uneducated guessing…prompted me to order some tip107’s last night. Should be here tomorrow.

Appreciate the help.

So…another question. The schematic says that Q97 is a TIP107. The one I pulled from the board has lettering scratched off, but the one next to it (Q98) clearly says TIP107. The parts list in the manual (see below) says 2N4403 PNP. Are these the same, interchangeable, or is the parts list wrong?

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Yes, seems that my manual is wrong. It is dated March 1997…just glad I double checked the markings on the actual transistors.

Swapped in a new tip107 in q97, and my lamp issues are solved. Thanks for the help